Folic Acid May Cut Colon Cancer Risk

Women who take a multivitamin pill containing folate once a day could significantly reduce their risk for colon cancer, according to researchers at Harvard University and Harvard-affiliated Brigham and Women's Hospital in Boston.

"Women who reported the highest intake of folate, through multivitamin use for at least 15 years, had a 75 percent reduced risk of colon cancer," said Edward Giovannucci, assistant professor of medicine at Harvard Medical School. "Women who took multivitamin supplements with folate for between five and ten years experienced a 20 percent reduced risk."

Folate, also known as folic acid, is plentiful in fruits, vegetables, orange juice, fortified cereals, and liver.

Previous studies at Harvard concluded that 400 micrograms of folate, together with three milligrams of vitamin B6, taken daily, cuts the risk of heart disease by a third. Both requirements can also be met by taking virtually any brand of multivitamin pill.

Another study found that 400 micrograms of folate a day cuts the risk of brain and spinal cord birth defects in half. Such research led the Food and Drug Administration to recently increase its recommended daily allowance of folate from 180 to 400 micrograms. Also, all wheat, corn, and rice breads, cereals, and pastas are now fortified with folate.

"Four hundred micrograms provides maximum protection against colon cancer," Giovannucci noted. "We cannot say for sure if higher doses would be any better. Even women who get more than 300 micrograms a day from fruits and vegetables benefit from taking multivitamin supplements. That might be because folate from supplements is better absorbed by the body than folate from fruits and vegetables."

This study was done with the help of 88,756 women who participated in the Nurses' Health Study, based at Brigham and Women's Hospital. However, "there is reason to believe that men would get similar benefits," Giovannucci added. In fact, another Harvard effort, the Health Professionals Follow-up Study, found that males in the health professions who took appropriate multivitamin pills for more than 10 years reduced their risk of colon cancer.

A detailed report on the women's study was published today in the Annals of Internal Medicine.

"Although our analysis shows that multivitamin supplements can reduce a women's risk of colon cancer by as much as 75 percent, supplements cannot be viewed as a panacea," Giovannucci cautioned. "A diet rich with fruits and vegetables is still important. The women who we determined to be at the lowest risk were those who combined sound nutritional habits with the use of multivitamin supplements."

How folate might reduce colon cancer incidence remains unknown. Giovannucci and his colleagues suspect the reason has to do with decreasing the likelihood of genetic mutations, aiding the repair of damaged genes, or protecting against errors when genes are copied during cell division.

However, it works: "for the vast majority of women and men it makes sense to take a multivitamin [pill] each day," advised Walter Willett, a professor of medicine and of nutrition at Harvard. "There is no known downside, and it provides a very inexpensive safety net."